Adds add_external_participants_from_cc to ServiceDeskSettings

Introduces a new database field that will allow maintainers
to toggle whether CCed email addresses should be
added as external participants on Service Desk issues

db/migrate/20231011150241_add_external_participants_from_cc_to_service_desk_settings.rb

+# frozen_string_literal: true
+
+class AddExternalParticipantsFromCcToServiceDeskSettings < Gitlab::Database::Migration[2.1]
+  enable_lock_retries!
+
+  def change
+    add_column :service_desk_settings, :add_external_participants_from_cc, :boolean, null: false, default: false
+  end
+end

db/schema_migrations/20231011150241

+92e1c02f769e19e0a0eb6a5e23d2ae54cb02d4d1e1d6d2532dca736ae3d97cee
\ No newline at end of file

db/structure.sql

@@ -23097,6 +23097,7 @@ CREATE TABLE service_desk_settings (
     encrypted_custom_email_smtp_password bytea,
     encrypted_custom_email_smtp_password_iv bytea,
     service_desk_enabled boolean DEFAULT true NOT NULL,
+    add_external_participants_from_cc boolean DEFAULT false NOT NULL,
     CONSTRAINT check_57a79552e1 CHECK ((char_length(custom_email) <= 255)),
     CONSTRAINT check_b283637a9e CHECK ((char_length(custom_email_smtp_address) <= 255)),
     CONSTRAINT check_e3535d46ee CHECK ((char_length(custom_email_smtp_username) <= 255))

spec/requests/api/project_attributes.yml

@@ -193,5 +193,6 @@ build_service_desk_setting: # service_desk_setting
     - encrypted_custom_email_smtp_password
     - encrypted_custom_email_smtp_password_iv
     - custom_email_smtp_password
+    - add_external_participants_from_cc
   remapped_attributes:
     project_key: service_desk_address